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    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
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<body>
    <script>
        var arr = [1,2,1,2,1,2,3];

        //set 自带去重功能
        var ste = new Set(arr)
        console.log(ste);
        // set 对象是长度
        ste.add("nn");
        console.log(ste.size);

        var arr1 = Array.from(ste);
        console.log(arr1);

        var map = new Map();
        console.log(map);

        map.set("name","lili")

        console.log(map.get("name"));
    </script>
</body>
</html>